Mechanical couplings for joining pipe elements end-to-end find widespread use throughout a broad spectrum of industries such as the chemical industry, the petroleum industry and mining, as well as in municipal water service and fire suppression systems for buildings and other structures.
An example of a prior art coupling currently in use is provided in U.S. Pat. No. 7,086,131, which discloses a coupling having a pair of coupling segments joined end-to-end by fasteners received in lugs at each end of the segments. A sealing member is positioned between the segments. The coupling is pre-assembled at the factory. The segments are designed and sized to receive pipe elements in the field which are inserted directly between the coupling segments in the pre-assembled state, without the need to disassemble and reassemble the coupling. After insertion of the pipe elements, the fasteners are tightened to effect a fluid-tight, mechanically restrained joint between the pipe elements.
While it is advantageous to pre-assemble such couplings because it saves time and thereby cost during construction, power tools are often used to tighten the fasteners for convenience, as they are faster and less fatiguing. Power tools are of limited value, however, where no source of electrical power or compressed air is available, even those tools which are battery operated. Furthermore, power tools which cause electrical sparking may not be used in environments, such as mines, where explosive conditions may exist. It would be advantageous to provide a pipe coupling which can be pre-assembled (and thereby secure the cost advantages and convenience of such couplings) while being easily manually tightened by workmen installing the couplings. It is further advantageous to decrease the stiffness of the joint formed by the coupling for certain applications. This can be accomplished by employing couplings according to the invention.